1. Field of the Invention
Embodiments of the disclosure relate in general to the field of computers and similar technologies, and in particular to software utilized in this field. Still more particularly, it relates to the management of serial attached small computer system interface (SAS) storage devices.
2. Description of the Related Art
Information processing systems continue to gain widespread adoption by many segments of today's modern society. At the same time, managing and protecting information is becoming more complex. This complexity is due in part to the need to store and access an ever increasing amount of information. As a result, the storage capacity of these systems must be continually updated, driving demand for larger, faster, and more reliable data storage systems. These updates are often costly and disruptive to users.
A variety of mass storage devices exist today, including hard disks, which continue to increase in performance and capacity, while simultaneously decreasing in size, power consumption, and cost. It has become common to use such disk drives in Redundant Array of Independent Disk (RAID) subsystems, which leverage commodity components to deliver cost-effective data storage redundancy and sustainability. However, the design attributes of the components typically used in these systems often limit their configuration and operating characteristics. One such limitation is when there is a mismatch between the physical configuration of a disk storage subsystem and the number of serial attached small computer system interface (SAS) target and initiator devices that a SAS expander or bridge device can support in a mixed mode configuration.
For example, a disk subsystem may comprise one or more disk storage enclosures, each of which can mechanically support sixteen storage devices. Each of the storage devices consumes a target device slot of the total number supported by the SAS expander or bridge device. Likewise, each enclosure management services device, such as a SCSI Enclosure Services (SES) device, also consumes a target device slot supported by the SAS expander or bridge device. Assuming that one SES device is used to manage sixteen (16) target devices, then an odd number of target device slots are consumed. Accordingly, if the number of target devices a SAS expander or bridge device can support is an even increment of sixteen (e.g., 64), then there is a resulting mismatch between the number of logically supported devices and the system's mechanical packaging configuration. In this example, if the SAS expander or bridge supports a total of 64 target devices, then there is a mismatch with the system mechanical configuration of 68 target devices (64 disk drive targets and 4 SES device targets). It will he appreciated that failure to align mechanical configurations with the logically supported configuration of the system creates the potential for human error, which in turn can lead to invalid or unsupported system configurations.